1. Field of the Invention
The present invention relates in general to a remotely positionable cleaning and inspection system. More particularly, it pertains to a modular wall crawler having a collapsible "H" shaped structure for boiler tube wall inspection and cleaning.
2. Description of the Related Art
The periodic inspection of internal tube walls in boilers has been accomplished traditionally by the use of personnel equipped with hand-held inspection devices. Access to these surfaces has been made possible by erecting appropriate scaffolding or the use of "sky climbers", "bosun's chairs", or similar devices to permit workers to position themselves properly in areas inaccessible by other means.
This approach is costly, time consuming, and hazardous to the personnel involved in the operation. Erection of the internal scaffolding or rigging for the other access modes mentioned cannot commence until the unit has cooled sufficiently to permit long-term entry by the personnel. The scaffold erection process and its subsequent removal involves personnel who should have no function in an inspection, and is thus an added expense throughout the outage.
U.S. Pat. No. 4,671,382 to D'Alessio, et al discloses such a scaffolding support assembly particularly useful as a base for modularized post-and-runner type scaffolding used on the interior of boilers or similar large interior spaces having sloping bottom walls for inspection, repair, maintenance, etc. The vertical uprights in the scaffold latticework have swivel bases, preferably of standard construction modified to accept stabilizing diagonals for tying into the balance of the scaffold latticework. The foot of the scaffold post rests, without attachments thereto, on a sloping surface, and is tied rigidly to a point on an adjacent scaffold post, thus securing the foot in position.
The height at which most of the tube inspection is done presents a significant personnel hazard. The environment in which it is done, particularly during the wall cleaning phase preparatory to the actual tube inspection efforts, is dirty and undesirable enough to prevent a team of skilled inspection technicians from functioning at top efficiency and productivity. Significant equipment is required to protect them from inhalation of damaging quantities of the materials dislodged from the tube walls.
A way to avoid the undesirable aspects of this work without appreciably increasing the cost of the inspection is needed.
U.S. Pat. No. 4,653,409 to Eriksson discloses an apparatus for regulating and cleaning air passages provided in the side wall of the furnace. The apparatus comprises a sleeve member reciprocatably mounted in the inner blocks and insertable into the air passage. The rear opening of the sleeve member connects to and is supported by a hollow section of an elongate holder which is slidably mounted in the longitudinal direction and extends through the wall of the air box. A driving device permits the apparatus to "poke" when necessary by pushing forward from its regulating position such that the inner end extends into the furnace for keeping the air passages clean. Furthermore, the hollow section of the holder has at least one air inlet which is substantially closed in its original position to prevent the admission of air into the air inlet. When the sleeve member is in the second or advanced position; the air inlet is outside the housing member to allow air from the air box to flow through the air inlet into the sleeve member.
This device is large and requires it to be fixed in one area of the furnace. It lacks the portability needed in boiler tube walls.
U.S. Pat. No. 4,241,609 to Bergman, et al discloses an internal measuring instrument for measuring the wall thickness of pipes and tubes which contain bends and curvatures along their length. The device also provides for detecting flaws within the tubes by using ultrasonic pulse/echo transducers. This internal inspection device requires access to the inner surface of the tube. Such a requirement would meet strong opposition in the power industry, especially for boiler waterwall tubes. Access to waterwall tubes is achieved through tube cutting or through water wall header inspection ports which are welded into place. The device comprises a rotatable disc support smaller in diameter than the interior diameter of the tube, wherein the disc is adapted to be snaked through the length of the tube.
Even though this apparatus is portable and requires a minimum of personnel, it lacks the flexibility of being able to function effectively in large areas as well as smaller ones. Also, it does not provide for cleaning the boiler tubes prior to or simultaneously with the inspection.
Therefore, there is a need for a remotely operable boiler tube wall cleaning and inspection system capable of being inserted through the boiler manway access ports and being positioned at will over the full area of the tube wall.